Bioconversion of Iminodiacetonitrile to Iminodiacetic acid with whole cells of Lysinibacillus boronitolerans MTCC 107614 (IICT-akl252).

Biotechnological potential of nitrilases are prompting significant interest in finding the novel microbes capable of hydrolyzing nitriles. In this view, we have screened about 450 bacterial strains for nitrilase production using bioconversion of iminodiacetonitrile (IDAN) to iminodiacetic acid (IDA) through hydrolysis and obtained six nitrilase-producing isolates. Among these six isolates, IICT-akl252 was promising which was identified as Lysinibacillus boronitolerans. This is the first report on L. boronitolerans for nitrilase activity. Optimization of various medium and reaction parameters for maximizing the nitrilase production using whole cells in shake flask was carried out for L. boronitolerans IICT-akl252. Sucrose (2 %) as a carbon source attained better nitrilase yield while IDAN appeared to be the preferable inducer (0.2 %). The maximum IDA formation was achieved with 100 mM IDAN and 150 mg/ml cells at 30 °C and pH 6.5. After optimization of the culture and reaction conditions, the activity of nitrilase was increased by 2.3-fold from 27.2 to 64.5 U. The enzyme was stable up to 1 h at 50 °C. The enzyme was able to hydrolyze aliphatic, aromatic and heterocyclic nitrile substrates.

Optimization of nitrilase production from Alcaligenes faecalis MTCC 10757 (IICT-A3): effect of inducers on substrate specificity.

Microbial nitrilases are biocatalysts of interest and the enzyme produced using various inducers exhibits altered substrate specificity, which is of great interest in bioprocess development. The aim of the present study is to investigate the nitrilase-producing Alcaligenes faecalis MTCC 10757 (IICT-A3) for its ability to transform various nitriles in the presence of different inducers after optimization of various parameters for maximum enzyme production and activity. The production of A. faecalis MTCC 10757 (IICT-A3) nitrilase was optimum with glucose (1.0%), acrylonitrile (0.1%) at pH 7.0. The nitrilase activity of A. faecalis MTCC 10757 (IICT-A3) was optimum at 35 °C, pH 8.0 and the enzyme was stable up to 6 h at 50 °C. The nitrilase enzyme produced using different inducers was investigated for substrate specificity. The enzyme hydrolyzed aliphatic, heterocyclic and aromatic nitriles with different substitutions. Acrylonitrile was the most preferred substrate (~40 U) as well as inducer. Benzonitrile was hydrolyzed with almost twofold higher relative activity than acrylonitrile when it was used as an inducer. The versatile nitrilase-producing A. faecalis MTCC 10757 (IICT-A3) exhibits efficient conversion of both aliphatic and aromatic nitriles. The aromatic nitriles, which show not much or no affinity towards nitrilase from A. faecalis, are hydrolyzed effectively with this nitrilase-producing organism. Studies are in progress to exploit this organism for synthesis of industrially important compounds.